Here is a pair of black/white Katanas which have a medium size blade and copper ends, plus a black sheath. Both swords can be crafted to be used as a normal sword or an off hand sword (held upside down like a Ninja or something).

Stats are similar to Ebony sword. Requires steel smithing to craft/improve and same materials as steel a sword.
Obtain by crafting or finding them in the basement of Dragonsreach. Weapon IDs are "katanamr", "katanamroffhand", "katanamrwhite" and "katanamroffhandwhite". No DLC required.

I would recommend not using the off hand versions in the player's right hand, since they they look rather silly when sheathed.

Mods in screenshots are from the Skyrim Nexus, 'Face Masks of Skyrim' by Volvaga0 and 'Dark Follower Armour' by Nockchaa.

To install simply extract files into Data folder in Skyrim's main folder.

If you prefer you can download through Steam here: http://steamcommunity.com/sharedfiles/filedetails/?id=219613545

If you are having problems leave a comment on the mod's Steam page and I'll try and help you.